X-ray generator



X-RAY GENERATOR Filed Oct. 2, 1941 INVENTOR5:-

02 z W u dv e 2 0W Patented Feb. 1, 1944 PATENT OFFICE X-BAY GENERATOR Zed J. Atlee, Elmhurst, and Howard W. Brackney, Chicago, Ill., as'signors to General Electric X-Ray Corporation, Chicago, 111., a corporation of New York Application October 2, 1941, Serial Nil/413,264 6 Claims. go1. of 147) This invention relates in general to roentgenology and has more particular reference to an X-ray generator having an improved window structure for the-emission of X-rays therethrough, the invention relating more especially 5; to an X-ray generator particularly well adapted for use in crystallography and, to that end, having a plurality of X-ray transmitting windows displaced angularly on the envelope with respect to the source of X-rays in the generator.

An important object of the present invention resides in providing, in an X-ray generator having an envelope and an anode forming a source of X-rays within the envelope, an improved window construction in the envelope to provide for the egress of 'X-rays substantially Without hindrance; a further object being to utilize a beryllium disk as a window means for the substantially unhampcred transmission of X-rays' therethrough; astill further object being-*to provide simple means for the'mounting of th beryllium disk on the envelope, which is usually of glass.

Another important object is to provide an improved X-ray generator particularly adapted for 7 use in crystallography, the generator comprising ifi anenvelope containing an anode forming a source of X-rays and the envelope being provided with a plurality of windows angularly displaced on the envelope with respect to the X-ray source, whereby rays transmitted through any of the windows may be utilized. i

Another important object is to provide an improvedX-ra window structure for X-ray generators bydrawing a neck forming a window opening in the envelope of the generator and by"- fixing a plateof material substantially transparcut to X-rays on said neck opposite the opening defined thereby; afurther object being'to utilize beryllium as a window-pan material substantiallytransparent to X-rays; a still further 40 I target material for X-ray difiraction analysis objectlbeing to provide for securing the beryllium' window element on the glass envelope material at saidneck; yet a further object bein to utilize a window mount comprising a ringlike element of "nickel steel, or other suitable mat-J teriah'io'r'I'nountin'g" the beryllium window ele- 'ment on the glass envelope. These and numerous otherimportant objects, advantages, and inherent functions of the invention will be fully understood from the follow-. --ing description,iwhich, taken inconnection with "the accomp'anying drawing, discloses a preferred embodiment of the invention. i V

"'Refe'rringtothe drawing:v r a of an X-ray tube embodying the present invention; and i Figures 2 and 3 are sectional views taken substantially along the, lines 22 in Figure 1 and 33 in Figure 2. V v. H

To illustrate theinvention, We hav shown on the drawing an X-ray generator II comprisin an anode structure l2 embodying a targetlfi, a cathode structure It embodying an electron source comprising a filament l5, and an envelope l6 enclosing the anode and cathode structures. The generator illustrated is particularly well adapted for crystallography, that is to say, the examination of materials by observation of'dif iractioncharacteristics when exposed to X-rays. Such analysis of materials may be accomplished by exposing the same toX-rays andrecording the X-ray diffraction characteristics of thematerial being examined; as by photographing the same on sensitized film. The radiation from an X-ray generator consists of a continuous, or white, spectrum, the wave length and intensity distribution of which depends largely upon the electrical potentials at which the generator is operated, it being under stood, of course, that X-rays are generated at the target l3 by impingement thereon of electrons emitted by the filament-J5. Electrons, in turn, are. emitted by thefilament when the same is electrically energized, as bythe flow of electrical current therethrough under the influence of electrical potential applied to the filament. Electrons emitted by the filament are caused to impinge upon th target l3 under the influence of electrical potential applied between the anode and the cathode filament. M U

The target l3 may comprise any preferred target material, such as tungsten, molybdenum, copper, nickel, cobalt, iron, chromium or other desired target material, the choiceof a suitable depending upon the type'of specimen to be examined, the particular technique employed, and the sort of information'sought. The X-ray spectrum of the rays producedby a generator depends upon the type of target material employed in'produc- 'type of target material employed. The spectra of the varioustarget materials are entirely-independentof the operating potential'of theg'en'er- A I a r 7' "ator above aiminimumvoltage, which minimum 1 Figure 1.is"a side view, partially: sectionalized,'5

voltage als'o is'characteristiciof the target mateunwanted X-rays.

rial. Any suitable tar-get material may, of course, be employed for X-ray diffraction analysis, provided, of course, the material of the target and hence its line spectrum is known, otherwise, the spectral lines caused by the target material in the spectrograph of the material being examined may be mistaken for lines supposedly caused by the test sample, and it will be obvious from the foregoing that the particular materials to be examined by difiraction may best be examined by using particular targets.

The target l3 may comprise a rectangular button set in the end of the target support afforded by the anode structure l2, and the anode structure I2 may be mounted in any suitable or preferred fashion in the envelope. Since the envelope preferably comprises a glass tube, the anode structure will ordinarily be mounted on a suitable envelope seal at one end of the envelope and thereby supported in place, and the cathode l4 preferably comprises a suitable head which may be supported and sealed upon a suitable envelope .seal at the other end of the envelope. Conductors for energizing the'electron producing filament l5 may extend outwardly of the envelope through the cathode seal, and the cathode end of the tube may be fitted with a ferrule I! carrying a base H! for connecting the filament conductors with a suitable external source of power for energizing the filament for electron emission.

It will be noted that the'filarnent is of elongated character and is'supported in a groove 2! formed in the cathode head. whereby electrons emitted by the filament, when energized, will be focused substantially along a line on the target parallel to the longitudinal axis of the filament. To aid in focusing the electron stream, the cathode structure may include a skirt-like shield 22 pro- ,iecting therefrom in position encircling the facing end of the anode, the target carrying end of the anode being immersed in said shield.

Any suitable source of external power may be used to cause electrons emitted by the filament l5 to impinge upon the target by connecting such external source of potential between one of the filament conductors and the anode stem 23 which is electrically connected through the anode structure with the target I 3 which extends outwardly of the envelope throu h the anode seal. The stem 23 may also contain. conduits 25 to provide for the circulation of a cooling fluid into and out of the anode structure from a suitable external source of cooling fluid. the interior of the cathode structure being preferably hollow o allow the cooling medium to circulate. therethrough and thereby carry off the heat generated at the anode as a result of electron impingement upon the target.

X-rays generated at the tar et as a. result of lectron impin ement thereon may travel in all directions outward y of the target in a zone exending substantially pt ri ht angles with respect to the longitudinal axis of the generator. In the interests of safety, it is desirable to permit only such rays as are required to escape outwardly of the envelope and, to this end, the envelope H preferably, though not essentially, comprises glass which is substantially impervious to X- rays in order to prevent egress of unusable and The envelope may comprise a hard glass of the borosilicate type, such as Corning No. 705 A. J which is substantially opaque to X-rays of the wave length of the K-alpha line of copper radiation, that is to say, the rays produced by activation of a copper anode.

The skirt-lik screen 22 also may have some X-ray screening eifect. In order to insure the retention of unwanted X-rays, we may, provide an annular sleeve 2'! upon the outer surfaces of the envelope opposite the target-carrying end of the anode, said sleeve preferably comprising the split parts 29 suitably clamped together around the envelope by means of suitable fastening screws 3!. This sleeve may comprise material opaque to X-rays for the purpose of confining within the envelope all except desired useful X- rays.

It is desirable, however, to allow all useful X-rays to have substantially unhampered exit from the X-ray source outwardly of the envelope. To this end, the envelope is formed with drawn necks 33 forming openings therein angularly displaced around the envelope with respect to the target [3, there being, in the illustratedembodimerit, four necks 33 relatively displaced by with respect to the target I3. The skirt-like shield 22 also is formed with perforations 35 in alignment with the envelope openings defined by the necks 33. Y

The space within the envelope, of'course, is necessarily maintained at low pressure, and in order to seal the envelope at the openings defined by the necks 33, we-provide window-panes 31 sealed on the necks 33 in'position closing the openings defined thereby. The panes 31 are disks or plates of material, such as beryllium, which is substantially transparent to X-rays so that useful rays may pass, freely and substantially without obstruction, from the source at the target I 3 outward through the panes -31. Beryllium, however, is difficultly scalable to glass, and in orcler to attach th pane elements 31 on the necks 33, we provide pane mounting elements 39 preferably comprising short sleeves or rings of suitable material, such as Fernico. One end of each mounting element 39 is sealed on the corresponding'neck 33, as by means of a glass-to-metal seal 4|, and the window element 31 is sealed at its edges in an annular seat 43 formed in the mountingelement 39, the beryllium disk 31 being sealed on the mounting element 39 as by silver solder brazing. r

The foregoing window structure provides not only a vacuum tight seal at'the envelope openings defined by the necks 33, but also afiords substantially unimpeded X-ray exit through the beryllium window-pane elements 31. The window structures comprising the necks 33, the mounting elements 39, and the substantially X- ray transparent pane 31, extend in corresponding openings 45 formed in the annular sleeve element 21, so that useful X-rays developed in the generator may, by operating the same, be made available at the outer ends of the openings 45.

While the window construction of our present invention is particularly well suited for use in a multiple window generator of the sort herein illustrated for crystallography, it will be obvious that the invention is not necessarily limited to a multiple window construction but may be used to advantage wherever X-ray transparent windows are required. i

It is thought that the invention and its numerous'attendant advantages will be fully understood from the foregoing description, and it is obvious that numerous changes may be made in the form, construction and arrangement of the several parts without departing from the spirit or scope of the invention, or sacrificing any of its attendant advantages, the form herein disclosed being a preferred embodiment for the purpose of illustrating the invention.

The invention is hereby claimed as follows:

1. An X-ray generator comprising a sealed envelope, anode and cathode means within said envelope, said envelope comprising a tubular glass portion surrounding said anode and having an opening therein opposite the anode, a metal mounting ring comprising an alloy including nickel as an alloy constituent thereof and having a coeflicient of expansion such as to permit said alloy to be sealed with glass and soldered to beryllium, said ring being sealed on said envelope at said opening, and a pane of beryllium sealed on said ring in position closing said opening.

2. An X-ray generator comprising a sealed envelope, anode and cathode means within said envelope, said envelope comprising a tubular glass portion surrounding said anode and having an opening therein opposite the anode, a metal mounting ring comprising an alloy containing nickel and iron sealed on the envelope at said opening, and a pane of beryllium sealed on said ring in position closing said opening.

3. An X-ray generator comprising a sealed envelope, anode and cathode means within said velope, anode and cathode means in said envelope, said envelope comprising a tubular glass portion surrounding said anode and having a plurality of openings formed therein and disposed opposite and radially with respect to the anode, a mounting ring comprising an alloy including nickel as an alloy constituent thereof and having a coefiicient of expansion such as to permit said alloy to be sealed with glass and soldered to beryllium, said ring being sealed to the envelope at each of said openings, and a plate of beryllium sealed in each of said rings.

5. An X-ray generator comprising a sealed envelope, anode and cathode means within said envelope, said envelope comprising a tubular glass portion surrounding said anode and having a plurality of openings formed therein and disposed opposite and radially with respect to the anode, a mounting ring comprising an alloy of nickel and iron sealed to said envelope at each of said openings, and a plate of beryllium sealed in each of said rings.

6. An X-ray generator comprising a sealed envelope, anode and cathode means within said envelope, said envelope comprising a tubular glass portion surrounding said anode and having a plurality of angularly displaced openings therein opposite and radially of said anode through which openings useful X ray beams may be projected from the anode in a plurality of directions radially of the anode, a metal mounting ring, said ring comprising a metal alloy including nickel as an alloy constituent thereof and having a coefficient of expansion such as to permit said alloy to be sealed with glass and soldered to beryllium, said ring being sealed to the envelope at each of said openings, and a pane of beryllium silver soldered to each of said rings.

ZED J. A'I'LEE. HOWARD W. BRACKNE'Y. 

